An aneurysm is a swelling of the aorta, the main blood vessel of the body. The aorta begins just above the heart and rises straight up in the front of the chest (ascending aorta) toward the top of the body. At that level, it takes a turn, called the aortic arch, toward the back of the body. From the aortic arch, the aorta runs along the spine all the way down the chest (descending aorta), through the diaphragm, and into the abdomen. In the mid-abdomen (abdominal aorta), just opposite the belly button, the aorta splits into two branches, each of which heads off to supply blood to one of the legs. The aorta, normally about 1 to 1-1/2 inches in diameter, gets smaller as it gives off branches in its course toward the lower body.

The ascending aorta gives off (supplies, as branches) the coronary arteries, which provide blood to the heart muscle itself. The aortic arch gives off all the important branches to the head, brain, and arms. The descending aorta gives off branches to each rib. The abdominal aorta gives off the branches to the liver, intestines, kidneys, and other important internal organs. Finally, each of the terminal branches of the abdominal aorta goes off to one of the legs. Each major segment of the aorta can develop an aneurysm. Aneurysms of the major segments of the aorta are illustrated in the figure. An aneurysm is a swelling of the aorta, so that the aorta bulges and becomes enlarged. Even the branches of the aorta can, at times, develop aneurysms. Sometimes, these bulges can have a shape reminiscent of the inner tubes that bulged through the wall of old, tube-type automobile tires.

Aneurysms are significant for one simple reason: they can rupture. A ruptured aneurysm often results in fatality, as blood is lost internally into the chest or abdominal cavities. Death can occur very quickly, at times within minutes or even seconds.

Sometimes, the patient can have pain related to aneurysm. For an aneurysm of the ascending aorta, the pain is usually felt behind the breastbone. For the descending aorta, the pain is usually felt in the high back, between the shoulder blades. For the abdominal aorta, the pain is usually felt in the lower back or flanks. The pain of an aneurysm is usually a nagging, aching pain, not brought on by any specific activity. Patients can usually differentiate the pain of an aneurysm from the pain felt in muscles, joints, and the spine, but they should consult their physician to help with this differentiation.

Unfortunately, most patients do not feel pain from an aneurysm until the moment it ruptures. That is the reason that detection and preemptive extirpation (removal) are of such importance.
At the specific moment of rupture, the patient feels an extremely severe pain, sharp and sudden. She may lose consciousness from internal bleeding. Death may occur very quickly. Sometimes, the internal layers of body tissues can contain the blood stream temporarily, giving a chance for prompt hospital transfer and surgical treatment.

If your aneurysm is causing pain over a period of time, it is likely that it will rupture. If your aneurysm is growing, it is likely that it will rupture.

Also, if your aneurysm has attained a certain size, we know that the chance of rupture increases. For the ascending aorta, if it grows to six centimeters in diameter, nearly three times the normal size, it is very likely to rupture. Extensive research at Yale University has shown that the chance of rupture or death from an aneurysm is 14 percent per year once the aneurysm attains a size of six centimeters. How big is six centimeters? A soft drink can has a diameter of 6.4 centimeters. So, if your aorta has reached a dimension about that of a soft drink can, you are at significant risk for a rupture.

Your aneurysm can be surgically removed and replaced by an artificial graft.

For patients too elderly or too feeble to undergo surgical removal of the aneurysm, internal grafts (called stents) can be delivered by catheter, without a major incision, in an effort to seal off the aneurysm from the bloodstream. This may help to prevent rupture in selected cases. Years of additional experience is needed to know if stent therapy effectively prevents rupture.

Aortic dissection is an internal split within the wall of the aorta. Blood under pressure gets into the wall of the aorta and splits that wall apart. Blood has gained access where it shouldn't be, but it has not-not yet, that is-perforated completely through the wall of the aorta.
This is the condition that affected Carmella in the story at the beginning of this section. Not surprisingly, as the aorta splits internally, the patient feels excruciating, knifelike, tearing pain. This pain is one of the most severe that a human being can ever feel. Aortic dissection, as in Carmella's case, is very serious.

Free rupture of a dissection can occur, leading to death from internal bleeding into a body cavity (pericardium, chest, or abdomen). Blood supply to internal organs can be disrupted by the dissection. In many cases, urgent surgery is required. As in Carmella's case, surgery can save the patient's life.

Up to this point, we have talked about aneurysms of the aorta. Aneurysms can indeed affect the heart itself. If you suffer a trans- mural, or through-and-through, heart attack, the involved muscle in that zone is dead. In some cases, that dead muscle becomes very thin and, over time, stretches out, producing a bulge very reminiscent of the bulge in an old-fashioned tube tire.

Now, aneurysms of the heart, unlike those of the aorta, never rupture. We do not know why they behave differently in this respect. However, aneurysms of the heart, of the left ventricle specifically, can cause trouble in a number of ways. They can cause heart failure by distorting the normal size, shape, and contraction pattern of your left ventricle-the vital pumping chamber of your heart. They can allow clots to form inside the bulging area-clots that can travel to dangerous parts of your circulation, such as the brain or the coronary arteries themselves. They can cause arrhythmias, as the neighboring tissue on the border of the aneurysm can be electrically unstable. And aneurysms can cause chest pain. In general, an aneurysm of the left ventricle is a bad thing to have. Outlook for these patients is among the poorest of any group with heart disease.

The good news is that aneurysms of the heart can be removed, usually in conjunction with a coronary artery bypass operation. Although we cannot restore muscle that has died, by removing the aneurysm we can restore the shape and size of the heart, improving the patient's outlook and preventing many of the complications of an aneurysm. Although it may sound dangerous to remove an aneurysm of the heart and suture and reshape the main pumping chamber, this procedure, since being pioneered by the preeminent heart surgeon Dr. Denton Cooley in 1958, has become quite safe and reproducible today.